DESCRIPTION: Based upon the work of the principal investigator and others over the past 20 years, the understanding of the red cell membrane skeleton (spectrin cytoskeleton) is highly advanced and provides the model to which other membranes are compared. Defects in the red cell membrane skeleton are known to underlie many forms of hemolytic anemia including spherocytosis and elliptocytosis. Interestingly, the investigator demonstrates that all known clinically important mutations in spectrin lie in regions of sequence divergence due to presumed functional importance. Nevertheless, understanding of the membrane skeleton is certainly not complete. The applicant proposes to identify new proteins which interact with spectrin and characterize sites of the interaction. The roles of selected functional domains of spectrin will be evaluated in cultured mouse erythroleukemia cells (MEL). The phenotypes of mutations in functionally important domains of skeletal proteins will be evaluated in transgenic mice. The three dimensional structure of certain functional domains will be solved by collaborative studies with nuclear magnetic resonance spectroscopy. These studies should enhance the current level of basic understanding of the membrane skeleton of normal and defective red cells and should provide insight into the membranes of complex nucleated cells.